show-stopper

/SH OW1 S T AA1 P ER0/
noun
  1. 1

    A performance or segment of a theatrical production that induces a positive audience reaction strong enough to pause the production.

  2. 2

    Any impediment that prevents all further progress; especially a software bug that must be fixed before any further development is possible.

Source: https://en.wiktionary.org/wiki/show-stopper, https://en.wiktionary.org/wiki/showstopper